Tech Articles '2020' 'January'

Many Jeep owners have discovered that the stock Dana 30 and 44 front axle housings under their vehicles are the weak links in an otherwise capable 4x4. While the factory D44 of the Wrangler JK Rubicon features stronger gears and axles, it, unfortunately, shares the same failure-prone axle tubes, inner "Cs," and cast center section of the D30 found in all other Wrangler, Cherokee, and Comanche models.

Issues with the stock D30/44 housings bending or even breaking can arise with moderate off-road use, especially when combined with 35-inch or larger tires.

At the heart of the Currie 44 lies a massively reinforced high-pinion nodular iron center section with additional material in critical areas, which delivers superior strength and rigidity (images below) over the stock housings.

Two models of the Curie 44 center section are offered. For Wrangler JK Rubicon direct replacement, a center section machined to accept the factory Rubicon electric locker and axles is available. For all other applications, a standard version is available that takes aftermarket lockers, such as those offered by ARB or Eaton. Regardless of the version ordered, both use the larger JK Rubicon D44 gears and axles for maximum strength.

Pressed and rosette welded into the center section are large 3-inch diameter .500 wall axle DOM tubes, which are more than twice as strong as the stock Dana 30/44 tubes without sacrificing ground clearance (image below).

Currie heavy-duty forged inner Cs are massively stronger than the stock D30/44 units and are designed for severe off-road use with up to 37-inch tires. To assure maximum strength, the knuckles are joined to the axle tubs with welds both inside and out (image below).

Complete bolt-in Currie 44 axle assemblies are available for Jeep Wrangler TJ, JK, Cherokee, and Comanche models as well as early Ford Bronco. Custom units are available for most applications.

When building a custom street rod or muscle car with driveline components from multiple sources, it is not uncommon to encounter u-joints of different sizes. Because your vehicle is now a custom application, going to the local auto parts store and looking up a u-joint by year-make-model won't work. But don't despair; with some simple measurements, it's possible to determine the required u-joints.

Most common driveshaft u-joints applications will use outside locks, where lugs (image 1) or snap rings (image 2) are used to secure and align the u-joint caps in the yoke.

Determining the u-joint series for external lock applications is a simple matter of measuring a few critical dimensions.

Measuring for Driveshaft U-joint Fitment

If you don't have the u-joint

1) Measure the distance between the lugs of the transmission and pinion yokes and the distance between the snap rings of the driveshaft yoke to attain the overall widths

2) Measure the yoke gap and the diameter at the cap location to get the cap diameters.

Make sure to check all of the width and diameter dimensions, as they may be different. If the dimensions do not match, you may require a conversion u-joint.

If you have the u-joint

1) Measure the outside distance across the u-joint (with caps installed)

2) Measure the diameter of the caps

Make sure to check all of the width and diameter dimensions, as they may be different.

Standard u-joints sizes are classified by series, with each series having specific cap diameter and overall joint width. Typically speaking, a higher series number translates to a stronger joint.

Standard U-joint Series, Dimensions and Part Numbers

*BC denotes Big Cap, a Ford creation with two thicker caps to resist the deformation caused by over-torquing of the u-bolt straps.

Conversion or combination u-joints include a mix of two different series specifications in the same joint so that that mismatched yokes and driveshafts can be connected. The caveat is that the joint is only as strong as the smaller series.

Conversion U-Joint Series, Dimensions and Part Numbers

 *BC denotes Big Cap, a Ford creation with two thicker caps to resist the deformation caused by over-torquing of the u-bolt straps.

Strength Ratings

U-joint strength depends on many factors, including material type, body design, the presence of a zerk fitting, cap size, etc. The chart below summarizes the continuous lifetime operating torque and yield torque values (the point at which the u-joint begins to deform)

U-Joint Series Torque Ratings

U-Joint Strap Kits

 *BC denotes Big Cap, a Ford creation with two thicker caps to resist the deformation caused by over-torquing of the u-bolt straps.